Description:Shares of Onyx Pharmaceutical soaring after it received- and rejected a $10 billion takeover offer from biotech Amgen. Its shares were already up 31 percent over the past 12 months. Onyx says Amgen's offer of $120 a share is too low. That offer represents a premium of 38 percent based on Onyx's closing price on Friday. And Onyx may have a point. Deutsche Bank analyst Robin Karnauskas says in a note: "From our M&A valuation, we expect higher bids for Onyx of at least $140."(0:56)